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gravitools.corrections

Corrections to a gravity signal

Sign of corrections

All corrections have to be subtracted from the measured gravity value.

STANDARD_ADMITTANCE = -3 module-attribute

Standard pressure admittance factor, in nm/s² per hPa

EOP_URL = 'https://datacenter.iers.org/data/csv/finals2000A.all.csv' module-attribute

Default URL to EOP data

EOP_PATH = Path.home() / '.config' / 'gravitools' / 'finals2000A.all.csv' module-attribute

Default path where EOP data is saved

eop_data = None module-attribute

Earth orientation parameter data

This is set automatically by read_eop_data().

read_eop_data(path=None)

Read EOP data from file

get_eop_data()

Read the EOP data from file, if it is not yet available

update_eop_data(expire='12h')

Request the EOP data file, if necessary

nominal_pressure(altitude)

Nominal pressure at given altitude.

Parameters:

  • altitude (float) –

    Location altitude, in meters.

Returns:

  • float –

    Nominal pressure, in hPa.

pressure_correction(p_atm, altitude, admittance=STANDARD_ADMITTANCE)

Gravity correction due to atmospheric pressure.

Parameters:

  • p_atm (float | Series | ndarray) –

    Atmospheric pressure values, in hPa.

  • altitude (float) –

    Location altitude, in meters.

  • admittance (float, default: STANDARD_ADMITTANCE ) –

    Pressure admittance factor, in nm/s^2 per hPa.

Returns:

  • float | Series | ndarray –

    Gravity correction, in nm/s².

effective_tilt(tilt_x, tilt_y)

Effective tilt angle, from X and Y angles

tilt_correction(g_raw, tilt_x, tilt_y)

Instrument tilt gravity correction.

Note that tilt_x and tilt_y are cast to float64, because float32 is insufficient precision.

Parameters:

  • g_raw (float) –

    Measured gravity value, in nm/s².

  • tilt_x (float) –

    Instrument tilt angle in X direction, in rad.

  • tilt_y (float) –

    Instrument tilt angle in Y direction, in rad.

Returns:

  • float –

    Gravity correction, in nm/s².

polar_motion_correction(pol_x, pol_y, lat, lon)

Gravity correction due to polar motion.

Reference: IAGBN Absolute Gravity Observations Documentation for BGI-Files (1992).

Parameters:

  • pol_x (float) –

    Polar motion X angle coorinate, in arcsec.

  • pol_y (float) –

    Polar motion Y angle coorinate, in arcsec.

  • lat (float) –

    Latitude of measurement site, in degree.

  • lon (float) –

    Longitude of measurement site, in degree.

Returns:

  • float –

    Gravity correction, in nm/s².

dg_polar(timeindex, lat, lon, eop=None)

Polar motion correction for a time series.

Parameters:

  • timeindex (DatetimeIndex) –

    Time index (UTC) for which to calculate the correction.

  • lat (float) –

    Latitude, in degree.

  • lon (float) –

    Longitude, in degree.

  • eop (DataFrame, default: None ) –

    Time series of polar motion coordinates.

Returns:

  • Series –

    Time series of polar motion correction, in nm/s².